This proposal is for purchase of an ultrahigh performance mass spectrometer for shared use primarily by Ohio State University faculty holding combined N.I.H. annual operating support of $1,987,972, for experiments that are not feasible with existing mass spectrometers on campus (see Project Description). The preferred instrument is a Fourier transform ion cyclotron resonance mass spectrometer, configured to include: 3 tesla superconducting solenoidal magnet, differentially pumped dual- cell, external electron source, array processor, Nd/YAG laser (including oscillator/amplifier and frequency doubler) and interface, and gas chromatograph and interface. The instrument will be shared among several research groups, for applications including (see Project Description): low-volatility compounds (all users), laser desorption/ionization (all users), ultrahigh mass resolution (Floss), MS/MS for ion structure determination (all users), gas-phase basicities and acidities (Paquette), and qualitative and quantitative analysis of heart drugs and their metabolites (Reuning, Robertson). The instrument will be operated on a service basis, and regular users from each research group will be trained for self-operation. The instrument will be installed maintained, operated, and updated by the OSU Campus Chemical Instrument Center (A.G. Marshall, Director).